Maternal cigarette smoking is the most important preventable cause of poor pregnancy outcomes in the U.S. and a leading cause of pediatric morbidity and mortality. Approximately 30% of women in the U.S. are cigarette smokers when they become pregnant and the prevalence is greater still among less educated women. About 80% of these women smoke throughout their pregnancy. Even among those who quit, 25-30% relapse during the pregnancy and 70% within 6 months of delivery. Efficacious interventions have been developed for promoting smoking cessation during pregnancy, but cessation rates are low, especially among low-income and highly nicotine-dependent women (< 15%). Efficacious interventions to prevent relapse during the postpartum period remain to be developed. . We propose to examine the efficacy of a voucher-based incentive program for promoting smoking cessation and preventing relapse during pregnancy and postpartum. This incentive program is efficacious in promoting and sustaining abstinence in cocaine and other illicit drug abusers. A recent trial suggested that vouchers may be efficacious for increasing smoking cessation among pregnant smokers. The proposed studies are designed to rigorously evaluate the efficacy of voucher-based incentives for promoting cessation and extend them to preventing relapse among pregnant women and new mothers. Two randomized trials are proposed. First, we will examine the efficacy of vouchers delivered contingent on smoking abstinence for increasing cessation rates during pregnancy and postpartum among 226 women who are still smoking at their first prenatal visit. Second, we will examine the efficacy of contingent vouchers for preventing relapse during pregnancy and postpartum among 96 women who have already quit smoking prior to the first prenatal visit. Women for both trials will be recruited from Vermont's largest obstetrical practice, which serves a large population of uninsured, low-income women. In both trials, the voucher-based intervention will be added to brief smoking advice delivered by physicians/midwives and compared against control conditions wherein brief advice is combined with vouchers delivered independent of smoking status. Overall, the proposed studies have the potential to contribute important new scientific and practical information on effective treatment for one of our nation's most daunting drug abuse problems.